Information About Multicast Routing

Multicast routing is a bandwidth-conserving technology that reduces traffic by simultaneously delivering a single stream of information to thousands of corporate recipients and homes. Applications that take advantage of multicast routing include videoconferencing, corporate communications, distance learning, and distribution of software, stock quotes, and news.

Multicast routing protocols delivers source traffic to multiple receivers without adding any additional burden on the source or the receivers while using the least network bandwidth of any competing technology. Multicast packets are replicated in the network by Cisco routers enabled with Protocol Independent Multicast (PIM) and other supporting multicast protocols resulting in the most efficient delivery of data to multiple receivers possible.

The ASA supports both stub multicast routing and PIM multicast routing. However, you cannot configure both concurrently on a single ASA.

Note The UDP and non-UDP transports are both supported for multicast routing. However, the non-UDP transport has no FastPath optimization.

Stub Multicast Routing

Stub multicast routing provides dynamic host registration and facilitates multicast routing. When configured for stub multicast routing, the ASA acts as an IGMP proxy agent. Instead of fully participating in multicast routing, the ASA forwards IGMP messages to an upstream multicast router, which sets up delivery of the multicast data. When configured for stub multicast routing, the ASA cannot be configured for PIM.

The ASA supports both PIM-SM and bidirectional PIM. PIM-SM is a multicast routing protocol that uses the underlying unicast routing information base or a separate multicast-capable routing information base. It builds unidirectional shared trees rooted at a single Rendezvous Point per multicast group and optionally creates shortest-path trees per multicast source.

PIM Multicast Routing

Bi-directional PIM is a variant of PIM-SM that builds bi-directional shared trees connecting multicast sources and receivers. Bi-directional trees are built using a DF election process operating on each link of the multicast topology. With the assistance of the DF, multicast data is forwarded from sources to the Rendezvous Point, and therefore along the shared tree to receivers, without requiring source-specific state. The DF election takes place during Rendezvous Point discovery and provides a default route to the Rendezvous Point.

NoteIf the ASA is the PIM Rendezvous Point, use the untranslated outside address of the ASA as the Rendezvous Point address.

Multicast Group Concept

Multicast is based on the concept of a group. An arbitrary group of receivers expresses an interest in receiving a particular data stream. This group does not have any physical or geographical boundaries—the hosts can be located anywhere on the Internet. Hosts that are interested in receiving data flowing to a particular group must join the group using IGMP. Hosts must be a member of the group to receive the data stream. For information about how to configure multicast groups, see the “Configuring a Multicast Group” section.

Multicast Addresses

Multicast addresses specify an arbitrary group of IP hosts that have joined the group and want to receive traffic sent to this group.

Clustering

Multicast routing supports clustering. In Layer 2 clustering, the master unit sends all multicast routing packets and data packets until fast-path forwarding is established. After fast-path forwarding is established, slave units may forward multicast data packets. All data flows are full flows. Stub forwarding flows are also supported. Because only one unit receives multicast packets in Layer 2 clustering, redirection to the master unit is common. In Layer 3 clustering, units do not act independently. All data and routing packets are processed and forwarded by the master unit. Slave units drop all packets that have been sent.

Licensing Requirements for Multicast Routing

The following table shows the licensing requirements for this feature:

Model

License Requirement

All models

Base License.

Guidelines and Limitations

This section includes the guidelines and limitations for this feature.

Context Mode Guidelines

Supported in single context mode. In multiple context mode, unshared interfaces and shared interfaces are not supported.

Firewall Mode Guidelines

Supported only in routed firewall mode. Transparent firewall mode is not supported.

IPv6 Guidelines

Does not support IPv6.

Additional Guidelines

In clustering, for IGMP and PIM, this feature is only supported on the master unit.

Enabling Multicast Routing

Enabling multicast routing lets you enable multicast routing on the ASA. Enabling multicast routing enables IGMP and PIM on all interfaces by default. IGMP is used to learn whether members of a group are present on directly attached subnets. Hosts join multicast groups by sending IGMP report messages. PIM is used to maintain forwarding tables to forward multicast datagrams.

Note Only the UDP transport layer is supported for multicast routing.

To enable multicast routing, enter the following commandperform the following steps:

Command

Purpose

multicast-routing

hostname(config)# multicast-routing

Enables multicast routing.

The number of entries in the multicast routing tables are limited by the amount of RAM on the ASA.

Configuring Stub Multicast Routing and Forwarding IGMP Messages

Note Stub multicast routing and PIM are not supported concurrently.

An ASA acting as the gateway to the stub area does not need to participate in PIM. Instead, you can configure it to act as an IGMP proxy agent and forward IGMP messages from hosts connected on one interface to an upstream multicast router on another interface. To configure the ASA as an IGMP proxy agent, forward the host join and leave messages from the stub area interface to an upstream interface.

To forward the host join and leave messages, enter the following command from the interface attached to the stub areaperform the following steps:

Step 5 To modify the specific interface from which you want to forward IGMP messages, select the interface and click Edit .

The Configure IGMP Parameters dialog box appears.

Step 6 From the Forward Interface drop-down list, choose the specific interface from which you want to forward IGMP messages.

Step 7 Click OK to close this dialog box, then click Apply to save your changes.

Configuring a Static Multicast Route

Configuring static multicast routes lets you separate multicast traffic from unicast traffic. For example, when a path between a source and destination does not support multicast routing, the solution is to configure two multicast devices with a GRE tunnel between them and to send the multicast packets over the tunnel.

When using PIM, the ASA expects to receive packets on the same interface where it sends unicast packets back to the source. In some cases, such as bypassing a route that does not support multicast routing, you may want unicast packets to take one path and multicast packets to take another.

Static multicast routes are not advertised or redistributed.

To configure a static multicast route or a static multicast route for a stub area, enter one of the following commandsperform the following steps:

Use the Add Multicast Route dialog box to add a new static multicast route to the ASA. Use the Edit Multicast Route dialog box to change an existing static multicast route.

Step 3 In the Source Address field, enter the IP address of the multicast source. You cannot change this value when editing an existing static multicast route.

Step 4 Choose the network mask for the IP address of the multicast source from the Source Mask drop-down list.

Step 5 In the Incoming Interface area, click either the RPF Interface radio button to choose RPF to forward the route or the Interface Name radio button, then enter the following:

In the Source Interface field, choose the incoming interface for the multicast route from the drop-down list.

In the Destination Interface field, choose the destination interface that the route is forwarded through from the drop-down list.

Note You can specify the interface or the RPF neighbor, but not both at the same time.

Step 6 In the Administrative Distance field, choose the administrative distance of the static multicast route. If the static multicast route has the same administrative distance as the unicast route, then the static multicast route takes precedence.

Step 7 Click OK .

Configuring IGMP Features

IP hosts use the Internet Group Management Protocol (IGMP) to report their group memberships to directly connected multicast routers.

IGMP is used to dynamically register individual hosts in a multicast group on a particular LAN. Hosts identify group memberships by sending IGMP messages to their local multicast router. Under IGMP, routers listen to IGMP messages and periodically send out queries to discover which groups are active or inactive on a particular subnet.

IGMP uses group addresses (Class D IP address) as group identifiers. Host group address can be in the range of 224.0.0.0 to 239.255.255.255. The address 224.0.0.0 is never assigned to any group. The address 224.0.0.1 is assigned to all systems on a subnet. The address 224.0.0.2 is assigned to all routers on a subnet.

When you enable multicast routing on the ASA, IGMP Version 2 is automatically enabled on all interfaces.

Note Only the no igmp command appears in the interface configuration when you use the show run command. If the multicast-routing command appears in the device configuration, then IGMP is automatically enabled on all interfaces.

This section describes how to configure optional IGMP setting on a per-interface basis and includes the following topics:

Disabling IGMP on an Interface

You can disable IGMP on specific interfaces. This information is useful if you know that there are no multicast hosts on a specific interface and you want to prevent the ASA from sending host query messages on that interface.

To disable IGMP on an interface, enter the following commandperform the following steps:

The Protocol pane displays Yes if IGMP is enabled on the interface, or No if IGMP is disabled on the interface.

Configuring IGMP Group Membership

You can configure the ASA to be a member of a multicast group. Configuring the ASA to join a multicast group causes upstream routers to maintain multicast routing table information for that group and keep the paths for that group active.

The Add IGMP Join Group dialog box allows you to configure an interface to be a member of a multicast group. The Edit IGMP Join Group dialog box allows you to change existing membership information.

Step 3 In the Interface Name field, choose the interface name from the drop-down list. If you are editing an existing entry, you cannot change this value.

Step 4 In the Multicast Group Address field, enter the address of a multicast group to which the interface belongs. Valid group addresses range from 224.0.0.0 to 239.255.255.255.

Step 5 Click OK .

Configuring a Statically Joined IGMP Group

Sometimes a group member cannot report its membership in the group because of some configuration, or there may be no members of a group on the network segment. However, you still want multicast traffic for that group to be sent to that network segment. You can have multicast traffic for that group sent to the segment by configuring a statically joined IGMP group.

Enter the igmp static-group command. The ASA does not accept the multicast packets, but instead forwards them to the specified interface.

In the main ASDM window, choose Configuration > Routing > Multicast > IGMP > Static Group to configure the ASA to be a statically connected member of a group. With this method, the ASA does not accept the packets itself, but only forwards them. Therefore, this method allows fast switching. The outgoing interface appears in the IGMP cache, but this interface is not a member of the multicast group.

To configure a statically joined multicast group on an interface, enter the following commandperform the following steps:

Command

Purpose

igmp static-group

hostname(config-if)#
igmp static-group group-address

Configures the ASA statically to join a multicast group on an interface.

The Access Group pane appears. The table entries in the Access Group pane are processed from the top down. Place more specific entries near the top of the table and more generic entries further down. For example, place an access group entry that permits a specific multicast group near the top of the table and an access group entry below that denies a range of multicast groups, including the group in the permit rule. The group is permitted because the permit rule is enforced before the deny rule.

Double-clicking an entry in the table opens the Add or Edit Access Group dialog box for the selected entry.

Step 2 Click Add or Edit .

The Add Access Group or Edit Access Group dialog box appears. The Add Access Group dialog box lets you add a new access group to the Access Group Table. The Edit Access Group dialog box lets you change information for an existing access group entry. Some fields may be dimmed when editing existing entries.

Step 3 Choose the interface name with which the access group is associated from the Interface drop-down list. You cannot change the associated interface when you are editing an existing access group.

Step 4 Choose permit from the Action drop-down list to allow the multicast group on the selected interface. Choose deny from the Action drop-down list to filter the multicast group from the selected interface.

Step 5 In the Multicast Group Address field, enter the address of the multicast group to which the access group applies.

Step 6 Enter the network mask for the multicast group address, or choose one of the common network masks from the Netmask drop-down list.

Step 7 Click OK .

Limiting the Number of IGMP States on an Interface

You can limit the number of IGMP states resulting from IGMP membership reports on a per-interface basis. Membership reports exceeding the configured limits are not entered in the IGMP cache, and traffic for the excess membership reports is not forwarded.

To limit the number of IGMP states on an interface, enter the following commandperform the following steps:

Command

Purpose

igmp limit number

hostname(config-if)# igmp limit
50

Limits the number of IGMP states on an interface.

Valid values range from 0 to 500, with 500 being the default value. Setting this value to 0 prevents learned groups from being added, but manually defined memberships (using the igmp join-group and igmp static-group commands) are still permitted. The no form of this command restores the default value.

Step 2 Choose the interface you want to limit from the table on the Protocol pane, and click Edit .

The Configure IGMP Parameters dialog box appears.

Step 3 In the Group Limit field, enter the maximum number of host that can join on an interface. Valid values range from 0 to 500. The default value is 500. Setting this value to 0 prevents learned groups from being added, but manually defined memberships are still permitted.

Step 4 Click OK .

Modifying the Query Messages to Multicast Groups

The ASA sends query messages to discover which multicast groups have members on the networks attached to the interfaces. Members respond with IGMP report messages indicating that they want to receive multicast packets for specific groups. Query messages are addressed to the all-systems multicast group, which has an address of 224.0.0.1, with a time-to-live value of 1.

These messages are sent periodically to refresh the membership information stored on the ASA. If the ASA discovers that there are no local members of a multicast group still attached to an interface, it stops forwarding multicast packet for that group to the attached network, and it sends a prune message back to the source of the packets.

By default, the PIM designated router on the subnet is responsible for sending the query messages. By default, they are sent once every 125 seconds.

When changing the query response time, by default, the maximum query response time advertised in IGMP queries is 10 seconds. If the ASA does not receive a response to a host query within this amount of time, it deletes the group.

To change the query interval, query response time, and query timeout value, perform the following steps:

Detailed Steps

Command

Purpose

Step 1

igmp query-interval seconds

hostname(config-if)# igmp query-interval
30

Sets the query interval time in seconds.

Valid values range from 0 to 500; 125 is the default value.

If the ASA does not hear a query message on an interface for the specified timeout value (by default, 255 seconds), then the ASA becomes the designated router and starts sending the query messages.

Step 2 Choose the interface you want to limit from the table on the Protocol pane, and click Edit .

The Configure IGMP Parameters dialog box appears.

Step 3 In the Query Interval field, enter the interval, in seconds, at which the designated router sends IGMP host-query messages. Valid values range from 1 to 3600 seconds. The default value is 125 seconds.

If the ASA does not hear a query message on an interface for the specified timeout value, then the ASA becomes the designated router and starts sending the query messages.

Step 4 In the Query Timeout field, enter the period of time, in seconds, before which the ASA takes over as the requester for the interface after the previous requester has stopped doing so. Valid values range from 60 to 300 seconds. The default value is 255 seconds.

Step 5 Click OK .

Changing the IGMP Version

By default, the ASA runs IGMP Version 2, which enables several additional features such as the igmp query-timeout and igmp query-interval commands.

All multicast routers on a subnet must support the same version of IGMP. The ASA does not automatically detect Version 1 routers and switch to Version 1. However, a mix of IGMP Version 1 and 2 hosts on the subnet works; the ASA running IGMP Version 2 works correctly when IGMP Version 1 hosts are present.

To control which version of IGMP is running on an interface, enter the following commandperform the following steps:

Configuring a Static Rendezvous Point Address

All routers within a common PIM sparse mode or bidir domain require knowledge of the PIM RP address. The address is statically configured using the pim rp-address command.

Note The ASA does not support Auto-RP or PIM BSR. You must use the pim rp-address command to specify the RP address.

You can configure the ASA to serve as RP to more than one group. The group range specified in the ACL determines the PIM RP group mapping. If an ACL is not specified, then the RP for the group is applied to the entire multicast group range (224.0.0.0/4).

To configure the address of the PIM PR, enter the following commandperform the following steps:

Command

Purpose

pim rp-address ip_address [
acl ] [
bidir ]

hostname(config)# pim rp-address
10.86.75.23 [
acl1 ] [bidir]

Enables or reenables PIM on a specific interface.

The ip_address argument is the unicast IP address of the router assigned to be a PIM RP.

The acl argument is the name or number of a standard ACL that defines with which multicast groups the RP should be used. Do not use a host ACL with this command.

Excluding the bidir keyword causes the groups to operate in PIM sparse mode.

Note The ASA always advertises the bidirectional capability in the PIM hello messages, regardless of the actual bidirectional configuration.

The Add or Edit Rendezvous Point dialog box appears. The Add Rendezvous Point dialog box lets you add a new entry to the Rendezvous Point table. The Edit Rendezvous Point dialog box lets you change an existing RP entry. Additionally, you can click Delete to remove the selected multicast group entry from the table.

These restrictions apply to RPs:

You cannot use the same RP address twice.

You cannot specify All Groups for more than one RP.

Step 3 In the Rendezvous Point Address field, enter the IP address for the RP.

When editing an existing RP entry, you cannot change this value.

Step 4 Check the Use bi-directional forwarding check box if the specified multicast groups are to operate in bidirectional mode. The Rendezvous Point pane displays Yes if the specified multicast groups are to operate in bidirectional mode and displays No if the specified groups are to operate in sparse mode. In bidirectional mode, if the ASA receives a multicast packet and has no directly connected members or PIM neighbors present, it sends a prune message back to the source.

Step 5 Click the Use this RP for All Multicast Groups radio button to use the specified RP for all multicast groups on the interface, or the Use this RP for the Multicast Groups as specified below radio button to designate the multicast groups to use with the specified RP.

Configuring the Designated Router Priority

The DR is responsible for sending PIM register, join, and prune messages to the RP. When there is more than one multicast router on a network segment, selecting the DR is based on the DR priority. If multiple devices have the same DR priority, then the device with the highest IP address becomes the DR.

By default, the ASA has a DR priority of 1. To change this value, enter the following commandperform the following steps:

Step 2 Choose the interface that you want to enable for PIM from the table on the Protocol pane, and click Edit .

The Edit PIM Protocol dialog box appears.

Step 3 In the DR Priority field, type the value for the designated router priority for the selected interface. The router with the highest DR priority on the subnet becomes the designated router. Valid values range from 0 to 4294967294. The default DR priority is 1. Setting this value to 0 makes the ASA interface ineligible to become the default router.

Step 4 Click OK .

Configuring and Filtering PIM Register Messages

When the ASA is acting as an RP, you can restrict specific multicast sources from registering with it to prevent unauthorized sources from registering with the RP. The Request Filter pane lets you define the multicast sources from which the ASA will accept PIM register messages.

To filter PIM register messages, enter the following commandperform the following steps:

The Request Filter Entry dialog box lets you define the multicast sources that are allowed to register with the ASA when the ASA acts as an RP. You create the filter rules based on the source IP address and the destination multicast address.

Step 3 From the Action drop-down list, choose Permit to create a rule that allows the specified source of the specified multicast traffic to register with the ASA, or choose Deny to create a rule that prevents the specified source of the specified multicast traffic from registering with the ASA.

Step 4 In the Source IP Address field, type the IP address for the source of the register message.

Step 5 In the Source Netmask field, type or choose the network mask from the drop-down list for the source of the register message.

Step 7 In the Destination Netmask field, type or choose the network mask from the drop-down list for the multicast destination address.

Step 8 Click OK .

Configuring PIM Message Intervals

Router query messages are used to select the PIM DR. The PIM DR is responsible for sending router query messages. By default, router query messages are sent every 30 seconds. Additionally, every 60 seconds, the ASA sends PIM join or prune messages.

To change these intervals, perform the following steps:

Detailed Steps

Command

Purpose

Step 1

pim hello-interval seconds

hostname(config-if)# pim hello-interval
60

Sends router query messages.

Valid values for the seconds argument range from 1 to 3600 seconds.

Step 2

pim join-prune-interval seconds

hostname(config-if)# pim join-prune-interval
60

Changes the amount of time (in seconds) that the ASA sends PIM join or prune messages.

Step 2 Choose the interface that you want to enable for PIM from the table on the Protocol pane, and click Edit .

The Edit PIM Protocol dialog box appears.

Step 3 In the Hello Interval field, type the frequency, in seconds, at which the interface sends PIM hello messages.

Step 4 In the Prune Interval field, type the frequency, in seconds, at which the interface sends PIM join and prune advertisements.

Step 5 Click OK .

Configuring a Route Tree

By default, PIM leaf routers join the shortest-path tree immediately after the first packet arrives from a new source. This method reduces delay, but requires more memory than the shared tree. You can configure whether or not the ASA should join the shortest-path tree or use the shared tree, either for all multicast groups or only for specific multicast addresses.

Use Shortest Path Tree for All Groups —Choose this option to use the shortest-path tree for all multicast groups.

Use Shared Tree for All Groups —Choose this option to use the shared tree for all multicast groups.

Use Shared Tree for the Groups specified below —Choose this option to use the shared tree for the groups specified in the Multicast Groups table. The shortest-path tree is used for any group that is not specified in the Multicast Groups table.

The Multicast Groups table displays the multicast groups to use with the shared tree.

The table entries are processed from the top down. You can create an entry that includes a range of multicast groups, but excludes specific groups within that range by placing deny rules for the specific groups at the top of the table and the permit rule for the range of multicast groups below the deny statements.

Configuring a Multicast Group

Multicast groups are lists of access rules that define which multicast addresses are part of a group. A multicast group can include a single multicast address or a range of multicast addresses. Use the Add Multicast Group dialog box to create a new multicast group rule. Use the Edit Multicast Group dialog box to modify an existing multicast group rule.

Step 2 The Rendezvous Point pane appears. Click the group that you want to configure.

The Edit Rendezvous Point dialog box appears.

Step 3 Click the Use this RP for the Multicast Groups as specified below radio button to designate the multicast groups to use with the specified RP.

Step 4 Click Add or Edit .

The Add or Edit Multicast Group dialog box appears.

Step 5 From the Action drop-down list, choose Permit to create a group rule that allows the specified multicast addresses, or choose Deny to create a group rule that filters the specified multicast addresses.

Step 6 In the Multicast Group Address field, type the multicast address associated with the group.

Step 7 From the Netmask drop-down list, choose the network mask for the multicast group address.

Step 8 Click OK .

Filtering PIM Neighbors

You can define the routers that can become PIM neighbors. By filtering the routers that can become PIM neighbors, you can do the following:

Prevent unauthorized routers from becoming PIM neighbors.

Prevent attached stub routers from participating in PIM.

To define neighbors that can become a PIM neighbor, perform the following steps:

Detailed Steps

Command

Purpose

Step 1

access-list pim_nbr deny router-IP_addr PIM neighbor

hostname(config)# access-list pim_nbr deny 10.1.1.1 255.255.255.255

Uses a standard ACL to define the routers that you want to have participate in PIM.

In the example, the following ACL, when used with the pim neighbor-filter command, prevents the 10.1.1.1 router from becoming a PIM neighbor.

Step 2

pim neighbor-filter pim_nbr

hostname(config)# interface GigabitEthernet0/3

hostname(config-if)# pim neighbor-filter pim_nbr

Filters neighbor routers.

In the example, the 10.1.1.1 router is prevented from becoming a PIM neighbor on interface GigabitEthernet0/3.

Choosing Permit allows the multicast group advertisements to pass through the interface. Choosing Deny prevents the specified multicast group advertisements from passing through the interface. When a multicast boundary is configured on an interface, all multicast traffic is prevented from passing through the interface unless permitted with a neighbor filter entry.

Step 5 In the IP Address text field, enter the IP address of the multicast PIM group being permitted or denied. Valid group addresses range from 224.0.0.0 to 239.255.255.255.255.

Step 6 From the Netmask drop-down list, choose the netmask for the multicast group address.

Step 7 Click OK .

Configuring a Bidirectional Neighbor Filter

The Bidirectional Neighbor Filter pane shows the PIM bidirectional neighbor filters, if any, that are configured on the ASA. A PIM bidirectional neighbor filter is an ACL that defines the neighbor devices that can participate in the DF election. If a PIM bidirectional neighbor filter is not configured for an interface, then there are no restrictions. If a PIM bidirectional neighbor filter is configured, only those neighbors permitted by the ACL can participate in the DF election process.

When a PIM bidirectional neighbor filter configuration is applied to the ASA, an ACL appears in the running configuration with the name interface-name _multicast, in which the interface-name is the name of the interface to which the multicast boundary filter is applied. If an ACL with that name already exists, a number is appended to the name (for example, inside_multicast_1). This ACL defines which devices can become PIM neighbors of the ASA.

Bidirectional PIM allows multicast routers to keep reduced state information. All of the multicast routers in a segment must be bidirectionally enabled for bidir to elect a DF.

The PIM bidirectional neighbor filters enable the transition from a sparse-mode-only network to a bidir network by letting you specify the routers that should participate in the DF election, while still allowing all routers to participate in the sparse-mode domain. The bidir-enabled routers can elect a DF from among themselves, even when there are non-bidir routers on the segment. Multicast boundaries on the non-bidir routers prevent PIM messages and data from the bidir groups from leaking in or out of the bidir subset cloud.

When a PIM bidirectional neighbor filter is enabled, the routers that are permitted by the ACL are considered to be bidirectionally capable. Therefore, the following is true:

If a permitted neighbor does not support bidir, then the DF election does not occur.

If a denied neighbor supports bidir, then the DF election does not occur.

If a denied neighbor does not support bidir, the DF election can occur.

To define the neighbors that can become a PIM bidirectional neighbor filter, perform the following steps:

Detailed Steps

Command

Purpose

Step 1

access-list pim_nbr deny router-IP_addr PIM neighbor

hostname(config)# access-list pim_nbr deny 10.1.1.1 255.255.255.255

Uses a standard ACL to define the routers that you want to have participate in PIM.

In the example, the following ACL, when used with the pim neighbor-filter command, prevents the 10.1.1.1 router from becoming a PIM neighbor.

Step 2

pim bidirectional-neighbor-filter pim_nbr

hostname(config)# interface GigabitEthernet0/3

hostname(config-if)# pim bidirectional neighbor-filter pim_nbr

Filters neighbor routers.

In the example, the 10.1.1.1 router is prevented from becoming a PIM bidirectional neighbor on interface GigabitEthernet0/3.

Choose Permit to allow the specified devices to participate in the DF election process. Choose Deny to prevent the specified devices from participating in the DF election process.

Step 6 In the IP Address text field, enter the IP address of the multicast PIM group being permitted or denied. Valid group addresses range from 224.0.0.0 to 239.255.255.255.255.

Step 7 From the Netmask drop-down list, choose the netmask for the multicast group address.

Step 8 Click OK .

Configuring a Multicast Boundary

Address scoping defines domain boundaries so that domains with RPs that have the same IP address do not leak into each other. Scoping is performed on the subnet boundaries within large domains and on the boundaries between the domain and the Internet.

You can set up an administratively scoped boundary on an interface for multicast group addresses by choosing Configuration > Routing > Multicast > MBoundary in ASDM entering the multicast boundary command. IANA has designated the multicast address range from 239.0.0.0 to 239.255.255.255 as the administratively scoped addresses. This range of addresses can be reused in domains administered by different organizations. The addresses would be considered local, not globally unique.

A standard ACL defines the range of affected addresses. When a boundary is set up, no multicast data packets are allowed to flow across the boundary from either direction. The boundary allows the same multicast group address to be reused in different administrative domains.

You can configure, examine, and filter Auto-RP discovery and announcement messages at the administratively scoped boundary by entering the filter-autorp keyword. Any Auto-RP group range announcements from the Auto-RP packets that are denied by the boundary ACL are removed. An Auto-RP group range announcement is permitted and passed by the boundary only if all addresses in the Auto-RP group range are permitted by the boundary ACL. If any address is not permitted, the entire group range is filtered and removed from the Auto-RP message before the Auto-RP message is forwarded.

To configure a multicast boundary, enter the following commandperform the following steps:

The MBoundary pane lets you configure a multicast boundary for administratively scoped multicast addresses. A multicast boundary restricts multicast data packet flows and enables reuse of the same multicast group address in different administrative domains. When a multicast boundary is defined on an interface, only the multicast traffic permitted by the filter ACL passes through the interface.

When the boundary filter configuration is applied to the ASA, the ACL appears in the running configuration with the name interface-name _multicast, where the interface-name is the name of the interface to which the multicast boundary filter is applied. If an ACL with that name already exists, a number is appended to the name (for example, inside_multicast_1).

Step 3 Choose the interface for which you are configuring the multicast boundary filter ACL from the Interface drop-down list.

Step 4 Check the Remove any Auto-RP group range check box to filter Auto-RP messages from sources denied by the boundary ACL. If the Remove any Auto-RP group range check box is unchecked, all Auto-RP messages are passed.

Step 5 Click OK .

Configuration Example for Multicast Routing

The following example shows how to enable and configure multicast routing with various optional processes:

Use the Add Multicast Route dialog box to add a new static multicast route to the ASA. Use the Edit Multicast Route dialog box to change an existing static multicast route.

Step 5 In the Source Address field, enter the IP address of the multicast source. You cannot change this value when editing an existing static multicast route.

Step 6 Choose the network mask for the IP address of the multicast source from the Source Mask drop-down list.

Step 7 In the Incoming Interface area, click either the RPF Interface radio button to choose RPF to forward the route or the Interface Name radio button, then enter the following:

In the Source Interface field, choose the incoming interface for the multicast route from the drop-down list.

In the Destination Interface field, choose the destination interface to which the route is forwarded through the selected interface from the drop-down list.

Note You can specify the interface or the RPF neighbor, but not both at the same time.

Step 8 In the Administrative Distance field, choose the administrative distance of the static multicast route. If the static multicast route has the same administrative distance as the unicast route, then the static multicast route takes precedence.

Additional References

Related Documents

Technical details about the IGMP and multicast routing standards used for implementing the SMR feature

IETF draft-ietf-idmr-igmp-proxy-01.txt

RFCs

RFC

Title

RFC 2113

IP Router Alert Option

RFC 2236

IGMPv2

RFC 2362

PIM-SM

RFC 2588

IP Multicast and Firewalls

Feature History for Multicast Routing

Table 30-2 lists each feature change and the platform release in which it was implemented. ASDM is backwards-compatible with multiple platform releases, so the specific ASDM release in which support was added is not listed.

Table 30-2 Feature History for Multicast Routing

Feature Name

Platform Releases

Feature Information

Multicast routing support

7.0(1)

Support was added for multicast routing data, authentication, and redistribution and monitoring of routing information using the multicast routing protocol.